Wow. $12 for everything. I should hook this up to a parallel port and see what happens. I found torque for a similar motor and it was an order of magnitude off from the nema17's we use even with the reduction. However, I think I can work with 1/10th the torque.

Also look at some of the other things they are offering. I see that they have an H-bridge driver setup for this motor also (costs a lot more, but should get 2x-4x the torque at speed. There are also You Tube videos about this motor for a teardown, operation, and how to convert it for H-Bridge operation and torque tests both ways. The only reason to get excited about this stepper is the cost (and small size). They are likely to wear out in a 3D printer, but if the replacement cost is $1, then just call it an expendable part and make it easy to replace.

With a motor this small and light, you could make the case for putting them on the arms. For making them go fast, you need an H-bridge driver and perhaps running everything on 24V to get the current rise faster at speed. The only issue would if they can take the heat. It would be interesting to base the whole printer design around the limitations of these motors.

I know that this motor can provide more torque at highr voltage, however I already readed some posts saying that the gearbox is very sloppy, and other posts saying that the exact angle of the steps (or steps/revolution) isn't constant even for motors of the same supplier.

Yes they are interesting, very low cost and promising, but I'm paranoid with the backlash.

I would substitute the gearbox with an anti-backlash one, but it would ruins the main reason you proposed that motor (its cost). I already tought about a stepper-servo (a planetary gearbox with an encoder, to have a closed-loop, high resolution, high torque and high speed blablabla but I need a 3d printer for test it...).

However I thought that the smal motor traveling inside the carriage with the gummy belt on the sides (like in the following picture) could compensate for backlash in lateral axis respect to travel, because of the gummyness of the belt (and if we could manage to insert an anti-backlash pulley - which is two pulleys with a preload - could be even better).

However I'm thinking about building a small LISA using M8 instead of torqsplines (i have 5 NEMA23 and a lot of 608ZZ/608RS ....) so If I could start to print I could be more helpful with you in developing the NICOLA.

@Nicholas Seward

Could you explain more about the design you proposed? I didn't understood much Right now I'm studying the LISA discussions and then I will do the same for GUS, I'm trying to understand if the NICOLA could be an even less expensive iteration of one of them.

@scipione205 Yes, the gears have play. However, I have seen videos and sample prints of the Tiko printer that uses these motors and there is no problem the way they designed it. So, there is a way to do it. I don't know the exact method they used, but all it takes is a bias such that the gears are always loaded in the same direction during operation. Generally speaking, that is not hard to do, but is simplest when you can let gravity be the spring load, like I expect they did. Their motor travels up and down a stationary rack. You can imagine how that loads the gears. If your goal is to make a good 3D printer, rather than the lowest cost 3D printer, then there are plenty of proven designs already. If you want to make your own design, then it will cost you 2x what you think the parts will cost (do to having to redesign more than once), and it will not work as good as others the first time, and it will take 4x - 8x as long as you imagine. It will take trying, experimenting, improving, more experimenting... etc., until you have success. This is how it always goes with inventing something new. As I said before, get your goals straight. Make sure you are striving for the goals you truly desire. Have no emotionally conflicting goals, or you will get nowhere.

I put this on hold because right now I found a FabLab at 40km away from my town, and thei allows me to use for free a Laser Cut router and a Sharebot NG (the SHarebot NG is an italian comemrcial printer - it has some issues but I can fix that), and now I will focus on realize a 3D printer and a CNC milling machine so I can be able to experiment an do reasarch without having to travel 40 Km every day.